For increasing the operating speed and integration level of integrated circuits, the sizes of the semiconductor devices are gradually decreased. For example, as the size of a CMOS IC is gradually decreased, the gate oxide layer becomes thinner and thinner. Consequently, the breakage voltage of the gate oxide layer is reduced, and the breakage voltage at the PN junction of the semiconductor device is also reduced.
As known, during the manufacturing process of the integrated circuit, an ESD zapping effect may lead to damage of the integrated circuit. For avoiding the ESD zapping effect, the integrated circuit is usually equipped with an ESD circuit. The ESD circuit provides an ESD current path. Since the ESD current flows through the ESD current path, the internal circuit of the integrated circuit is not damaged by the ESD current.